1. Technical Field
The present invention relates to a tunable capacitance control circuit and a tunable capacitance control method which is used in an integral circuit (IC), or the like, and more particularly, to a tunable capacitance control circuit and a tunable capacitance control method capable of increasing a Q (Q=1/RC) factor by reducing a total field effect transistor (FET) on-resistance value as compared to a scheme according to the related art using a control scheme of switching on only one of N FET switches configuring a unit cell and switching off other FET switches thereof.
2. Description of the Related Art
In accordance with the development of an efficient communication system, a plurality of communication standards having different operation frequencies and modulation schemes have been applied. Since various standards include a form in which a plurality of independent signal paths are coupled in parallel with each other, a size and a cost of a circuit increase. If a resettable circuit may be designed, the cost and the size of a parallel circuit may decrease. Therefore, research into an adaptive radio frequency (RF) circuit has recently been conducted.
The RF circuit may be generally divided into two regions, that is, a receiver and a transmitter. A receiver path has been successfully implemented so as to be tunable. However, a transmitter path has not been implemented so as to be tunable. Since a tunable capacitor or inductor capable of maintaining its characteristics even at high power is essentially required, it is difficult to implement the transmitter path, in particular, a power amplifier. If tunable components may be used in a high power application field, performance of the transmitter, in particular, the power amplifier may be significantly improved.
In accordance with the development of a wireless communication technology, fourth generation (4G) mobile communication representative of long term evolution (LTE) as well as current third generation (3G) mobile communication is emerging. As 4G mobile communication network functions are added to the existing 3G mobile communication network, a scheme to be supported in a single mobile phone become increase. In relation to this, the following functions are required for the current RF performance.
1) There is a need to cover various frequency bands using a single RF chain.
2) There is a need to optimize matching of a front-end including an antenna during the use of the mobile phone to optimize power consumed in the power amplifier (PA).
3) There is a need to optimize the matching of the front-end including the antenna during the use of the mobile phone to optimize a receiving rate of a low noise amplifier (LNA).
In order to implement the functions as described above, there is a need to add a tunable matching network (TMN) to the RF front-end having the existing fixed structure to add flexibility. Here, a tunable component is used for tunable performance. As the tunable component, a tunable capacitor has been used. In this case, in order to reduce loss of a system, a Q (Q=1/RC) factor of the tunable capacitor should be excellent.